Model hydrogeologiczny Centralnego i Północnego Okręgu Węglowego w Lubelskim Zagłębiu Węglowym

Abstract

Scharakteryzowano warunki hydrogeologiczne Centralnego i Północnego Okręgu Węglowego LZW. Podano parametry pięter wodonośnych kredy, jury i karbonu. Wskazano na pionową strefowość hydrochemiczną, podano wyniki badań izotopów stałych w wodach. Dokonano próby interpretacji w zakresie wieku wód oraz określono drogi ich krążenia w skali regionalnej.

HYDROGEOLOGICAL MODEL OF CENTRAL AND NORTHERN COAL FIELDS IN THE LUBLIN COAL BASIN

The paper presents hydrogeological model of the Central and Northern Coal Fields in the Lublin Coal Basin versus regional hydrogeological conditions (Fig. 1).

Four main water-bearing stages distinguishable in the hydrogeological section of this area include Quaternary, Cretaceous, Jurassic and Carboniferous (Figs. 2, 3). Figure 3 shows hydrogeological parameters of these stages.

Layered aquifers with water table usually not under pressure occur in the hydrogeological profile of the Quaternary water stage.

Cretaceous water stage is represented by Upper and Lower Cretaceous aquifers. In the case of the Upper Cretaceous, rock series characterized by increased permeability and water-bearing capacity appear confined to the uppermost parts, down to about 200 m depths, whereas underlying Upper Cretaceous rocks are practically impervious. Fissure-layered Lower Cretaceous aquifer is formed by Albian sandstones and conglomerates. This aquifer, often of the quicksand nature, is carrying out waters at the pressure of about 55 atm.

Jurassic water-bearing stage is formed by limestone complex about 100 m in thickness and carrying out fissure-karst waters at the pressure of about 65 atm.

Water-bearing capacity of Westphalian deposit series is related to sandstone intercalations forming independent fissure-layered aquifers which carry out waters at the pressure of 65–85 atm. Sandstones from uppermost members of the Westphalian are more permeable and water-bearing than the underlying ones.

Hydrochemical zonality of groundwaters of the Lublin Coal Basin is expressed by increase of total mineralization along with depth and the following succession of chemical types of waters marked along the circulation routes: HCO₃® HCO₃–CI®CI–HCO₃®Cl. The increase in mineralization and changes in ionic composition of waters are consistent with strike of strata and regional direction of water flow (from east to west).

The studies on chemical, gas and isotope (d¹⁸0, dD, T, ¹⁴C) composition of waters showed that there are 2 main hydrogeochemical environments in the Lublin Coal Basin. One environment comprises blanket and deposit series occurring at depths to about 1000 m. It is characterized by waters of the HCO₃, HCO₃-Cl and Cl–HCO₃ types and mineralization usually below 5 g/l. Stable isotope ratios range from -10.14 ¸ –8.4‰ (d¹⁸0) and –71.79 ¸ –60.0‰ (6D). The ¹⁴C age of waters from the Jurassic and Carboniferous aquifers ranges from a few to about 30 000 years.

The other hydrogeochemical environment is related to lower members of the Carboniferous and Devonian. Stronger mineralized waters occurring here are isolated from the influence of atmospheric waters.

Carboniferous aquifers are indirectly supplied by waters coming from Jurassic water-bearing stage which, in turn, is supplied by Cretaceous aquifers mainly in the eastern part of this area (Fig. 2).